The present invention relates to the clamps of drilling tool for machining, and in particular to a tool chuck.
When the tools such as a machine tool and an electric drill are used for the operation of drilling, milling and the like, a tool chuck is often used to clamp and locate a tool bit to improve the accuracy of drilling or milling. The tool chuck is usually comprising a chuck body, a plurality of jaws, a sleeve and a screw nut fixedly connected to the sleeve, the jaws are disposed in an inclined hole designed in the chuck body, and the jaws are driven to moves towards and away from the axis of the chuck body via the relative rotation between the chuck body and the sleeve, thereby realizing the clamping and releasing of the tool bit. However, in actual operation, in order to ensure that the tool bit is in the center of a clamping part, an operator often has to hold the tool bit with hand or other holding tool till the clamping jaws applies a certain action force to the tool bit, which is very inconvenient. More particularly when the size of the tool bit is smaller, the moving distance of the clamping jaws is bigger, the operator needs to hold the tool bit for long time for aligning and centering. Besides, in a bad working condition, the operation flexibility of the user is reduced, it is hard to align the tool bit with the clamping part of the drill chuck rapidly and then the operator has to repeat the operation again and again, and both time and labor are wasted. During a chuck mode of an auto chuck in which a motor drive the chuck body to rotate relative to the sleeve, the tool bit is easily impacted to be directly thrown out to injure the operator who holds tool bit.
In prior art, the CN patent CN100493788C discloses a rapidly pre-tightened drill chuck, comprising a chuck body, three jaws and a screw nut. An axial hole jointed with the drive shaft of a drill tool designed in the rear end of the chuck body. The shank portion of a tool bit is disposed in the front axial hole designed in the front end of the chuck body. The three jaws are respectively mounted in three inclined holes equidistantly disposed on the chuck body. The screw nut meshes with the three jaws. Three spring leaves are equidistantly disposed on the front axial hole adjacent to the three jaws. The three spring leaves and the three jaws are distributed at an interval of 60 degrees away from central lines of the three jaws, the center of the three spring leaves is located in a central axis of the axial hole in the front end of the chuck body, the front ends of the three spring leaves are naturally closed, the axial hole in the front end of the chuck body is further internally provided with a sleeve fixedly connected thereto, and the three spring leaves are fixed on the front end of the sleeve. By arranging the spring leaves, when the tool bit is replaced, a clamping handle of the tool bit can be directly inserted into a clamping opening formed by the spring leaves, and the tool bit is naturally clamped and aligned by an elastic force of the spring leaves per se without a need to hold the tool bit by hand.
Another CN patent CN 101284378A discloses a handheld power tool, comprising a tool chuck, at least one jaws of the chuck is provided with a magnet and the rear end of the tool bit is also provided with a magnet, so that the tool bit can be attached to the jaws by the action of the magnetic force between the two magnets on the jaw and the tool bit. By disposing the magnets on the jaw and the tool bit, the adsorption force between the jaw and the tool bit are enhanced.